The invention concerns an infinitely variable toroidal drive.
Those infinitely variable toroidal drives usually have, co-axially disposed in relation to a common shaft, input and output discs which are arranged in pairs and have toroidal-shaped inner surfaces, friction wheels situated between the pairs of input and output discs. The friction wheels are in frictional contact both with the input discs and with the output discs and transmit the torque that has been transmitted to them by the input disc to the output disc by frictional contact, the rotational speed of the friction wheels being higher as greater is the distance between their contact point with the input disc and the axis of rotation. On the other hand, the rotational speed of the output disc is higher as nearer the contact point is between friction wheel and output disc to the axis of rotation. Accordingly, the rotational speed of the output disc can be infinitely and arbitrarily set by swiveling the friction wheels. To this end, the axes of rotation of the friction wheels are supported on a carrier which can be controlled via a swiveling device.
The basic principle of such infinitely variable toroidal drives has already been described in U.S. Pat. No. 2,152,796 published in the year 1939. In this publication are provided two pairs of concave input and output discs between which are disposed swiveling supported friction wheels so that a torque, transmitted via an input shaft to the input discs, and the friction wheels, according to the relative position of the friction wheels with a reduction ratio depending thereon, is fed via the input discs, a gear wheel step and a hollow shaft to a compound gear in the form of a planetary transmission. The web of the planetary transmission drives an output shaft which is connected with the input gears, e.g. of a motor vehicle. At the same time, the output shaft can be disposed parallel to and spaced from the output shaft. The output gear wheel and the two output discs are rotatably supported on a sleeve which, on its ends, is supported in bearing brackets. The arrangement of the bearing brackets between respective input and output shafts presupposes a sufficiently large installation space between the discs.
The transmission according to U.S. Pat. No. 3,739,658 also has a pull-and-push variator with two input and output discs arranged in pairs between which are situated tiltingly supported friction wheels. This construction includes a bearing bracket which is component part of the housing and spatially is horizontally placed between the two output discs. The power flowing from the output discs is fed to a hollow shaft via a planetary transmission that, in addition, acts as differential. The hollow shaft is non-rotatably connected with an output gear wheel and is rotatably retained by the ball bearings in bearing bracket.
The output gear wheel is drivingly connected with a gear wheel which is non-rotatably fastened on the housing of a torque converter. The latter drives the output shaft of the transmission. The arrangement of the torque converter on the input of the output shaft implies a relatively large axial distance between input and output shafts of the transmission. Thus, the occasions for use of the transmission are strictly limited, since the required installation space is not always available.
U.S. Pat. No. 4,893,517 has disclosed an infinitely variable toroidal drive having an input shaft that penetrates a housing. The housing is divided by a partition wall in two hollow spaces in each of which are situated an input disc and an output disc opposite each other with friction wheels therebetween, both the input disc and the output disc lying in both hollow spaces on a common axis toward which the friction wheel can be swung to attain the desired speed ratio. The two pairs of input discs and output discs are disposed in mirror symmetry to each other in both hollow spaces so that both output discs are next to each other, specifically at both sides of the partition wall separating from each other the two hollow spaces and in which a gear wheel is supported which is actuated with the output torque jointly by both output discs.
The torque is transmitted, via another gear wheel to the parallel output shaft thereby to penetrate only one of the two hollow spaces and be supported on the partition wall on one end.
The partition wall, together with the appertaining bearings and spacers, can be introduced in the housing and bolted therewith as a pre-assembled unit, however the possibility of pre-assemblage is limited to a few individual parts; therefore, the assembly cost for completing the transmission is still considerable. Another disadvantage of this transmission consists in that very strong forces are introduced in the transmission housing, which makes necessary strong construction with corresponding heavy weight.
U.S. Pat. No. 5,033,322 also has described an infinitely variable toroidal drive, having basically the same design as the above described toroidal, i.e. two transmission units each in the form of an input disc, an output disc and friction wheels pivotably supported therebetween. In order to prevent in such a toroidal drive, whenever one transmission unit is controlled by the control device, the carriers for the friction wheels of the other transmission unit being exposed to vibrations, a mechanical device is provided in this known toroidal drive which prevents the reciprocal movement of the first pair of carriers for the friction wheels and the second pair of carriers for the friction wheels. The device consists of upper and lower transverse links (i.e. yokes), which accommodate the bearings for the carriers (pivots) of the friction wheels and which are swingingly disposed around pivots fastened to the housing. In order to eliminate a relative movement to each other, the transverse links are rigidly interconnected by rods extending in longitudinal direction. Vibrations, acting upon the carriers due to the friction wheels, are limited so that the slip on the second transmission unit is reduced.
In the toroidal drive according to the U.S. Pat. No. 4,934,206, the output gear wheel is supported on one side by bearings in a partition wall and on it other side is connected to an output disc. For this connection, the output gear wheel is provided with a collar which, via a spline, provides a non-rotatable support and fastening of the other output disc on the output gear wheel. With strong torques, the non-rotatable connection of the output disc to the output gear wheel proves inadequate. Also the support of the output disc directly upon the transmission main shaft is unfavorably affected, since eccentricities are inevitable between the support and the outer diameter of the collar on the output gear wheel.
The invention is based on the problem of supporting and disposing the output shaft and the gear wheel fastened thereon so as to make possible easy assembly and a compact design.